Article (Scientific journals)
Excitation of the FUV Io tail on Jupiter: Characterization of the electron precipitation
Gérard, Jean-Claude; Gustin, Jacques; Grodent, Denis et al.
2002In Journal of Geophysical Research. Space Physics, 107 (A11)
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Keywords :
Io; flux tube; ultraviolet spectroscopy; Jupiter; electron energy; slippage
Abstract :
[en] [1] Spectral observation of both polar regions of Jupiter in the far ultraviolet (FUV) obtained with the Space Telescope Imaging Spectrograph (STIS), on board the Hubble Space Telescope from July 1997 to January 2001 have been combined with FUV images to map the FUV color ratio along the STIS slit. Spatially resolved spectra of the aurora carried at similar to12 Angstrom resolution have been used to determine the amount of methane absorption as measured by the FUV color ratio of the Io magnetic footprint and its trailing tail. It is found that the absorption is systematically less than in the main polar aurora, indicating a higher altitude source region. The color ratio of the north tail is shown to slowly decrease downstream from the footprint. The combination of these spectral data with a two-stream model of the interaction of energetic electrons with the Jovian thermosphere indicates that the mean energy of the electrons creating the north FUV emission ranges from similar to55 keV at the Io footprint to similar to40 keV, 20 degrees downstream in the tail. In parallel, the incident electron energy flux drops by a factor similar to6 over the same angular distance. These observations are consistent with the steady state slippage picture where the subcorotating flux tube is accelerated very slowly up to corotation owing to the nonideal coupling. It is argued that small deviations from corotation can supply sufficient energy to fuel the observed auroral emissions. It is suggested that the parallel electric field accelerating electrons out of the flux tube only moderately depends on the time elapsed since the contact with Io, although the mapping between a point in the tail and Io is very uncertain in the presence of magnetic field line slippage.
Disciplines :
Earth sciences & physical geography
Author, co-author :
Gérard, Jean-Claude  ;  Université de Liège - ULiège > Département d'astrophys.
Gustin, Jacques ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Labo de physique atmosphérique et planétaire (LPAP)
Grodent, Denis  ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Labo de physique atmosphérique et planétaire (LPAP)
Delamere, P.
Clarke, J. T.
Language :
English
Title :
Excitation of the FUV Io tail on Jupiter: Characterization of the electron precipitation
Publication date :
November 2002
Journal title :
Journal of Geophysical Research. Space Physics
ISSN :
2169-9380
eISSN :
2169-9402
Publisher :
Amer Geophysical Union, Washington DC, United States
Volume :
107
Issue :
A11
Peer reviewed :
Peer Reviewed verified by ORBi
Available on ORBi :
since 06 March 2009

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